<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/01/04/changing-the-background-alpha-of-a-horizontallist-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        creationComplete="init();" viewSourceURL="srcview/index.html">

    <mx:Style>
        Application {
            backgroundGradientColors: red, black;
        }
    </mx:Style>

    <mx:Script>
        <![CDATA[
            import mx.events.SliderEvent;

            private function init():void {
                slider.value = horizontalList.getStyle("backgroundAlpha");
            }

            private function slider_change(evt:SliderEvent):void {
                horizontalList.setStyle("backgroundAlpha", evt.value);
            }
        ]]>
    </mx:Script>
    
    <mx:Array id="arr">
        <mx:Object label="Accordion" />
        <mx:Object label="ApplicationControlBar" />
        <mx:Object label="Box" />
        <mx:Object label="Canvas" />
        <mx:Object label="ControlBar" />
        <mx:Object label="DividedBox" />
        <mx:Object label="Form" />
        <mx:Object label="FormHeading" />
        <mx:Object label="FormItem" />
        <mx:Object label="Grid" />
        <mx:Object label="HBox" />
        <mx:Object label="HDividedBox" />
        <mx:Object label="Panel" />
        <mx:Object label="TabNavigator" />
        <mx:Object label="Tile" />
        <mx:Object label="TitleWindow" />
        <mx:Object label="VBox" />
        <mx:Object label="VDividedBox" />
        <mx:Object label="ViewStack" />
    </mx:Array>
    
    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="backgroundAlpha:">
                <mx:HSlider id="slider"
                        minimum="0.0"
                        maximum="1.0"
                        liveDragging="true"
                        tickInterval="0.1"
                        change="slider_change(event);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>
    
    <mx:HorizontalList id="horizontalList"
            dataProvider="{arr}"
            backgroundAlpha="1.0"
            backgroundColor="haloSilver"
            columnWidth="175"
            columnCount="3"
            rowCount="1"
            rowHeight="100" />
    
</mx:Application>